1. Field of the Invention
The present invention relates to load handling vehicles, and in particular to such vehicles with a bucket and a mechanism for tilting the bucket with respect to horizontal.
2. Description of the Prior Art
A number of prior art load handling vehicles having buckets or blades are known to have a mechanism for tilting the bucket with respect to horizontal.
Among such tilt mechanisms are those of the type having a pair of side arms rigidly connected together by a crossbar to form a fixed H-frame framework. The arms are each pivoted at a first end to the body of the vehicle and pivoted at their opposite or second end to the bucket. A short stroke hydraulic cylinder is connected at one end to the bucket and at its other end to one of the arms. Also, a rigid link is connected at one end to the bucket and its other end to the other arm. With this construction, operation of the short stroke cylinder applies a torsional load to the bucket and physically twists it. This racking or twisting of the bucket tilts it with respect to horizontal. However, because of the repeated physical twisting, such buckets are subject to breakage and fatigue failure. Furthermore, the buckets are relatively expensive to construct because reinforcing and heavier components must be utilized to withstand the torsional stresses applied to the bucket during tilting.
In another known type of prior art tilt mechanism, a bucket is pivotally connected to the body of a vehicle by an H-frame framework which includes a pair of arms and a cross-member. In addition, a hoist cylinder is connected at one end to a first of the arms and at its other end to the vehicle body while another hoist cylinder extends between the other arm and vehicle body. Simultaneous extension and retraction of these hoist cylinders respectively lowers and raises the framework and hence, the bucket. Also, in this device, the bucket is tilted by extending one hoist cylinder while simultaneously retracting the other hoist cylinder. This physically twists both the H-frame framework and the bucket and causes the bucket to tilt. A cam actuated air switch is provided to control the hoist cylinders to limit the maximum tilt of the bucket. In addition, the cross-member is pivoted at its respective ends to the side arms to twist as the bucket is tilted to partially take up stresses applied to the framework during tilting.
However, in common with the other prior art devices, this particular mechanism highly stresses the bucket. Consequently, the bucket is subject to failure and must be heavily constructed to withstand the torsional loading applied to it during tilting. Furthermore, vehicles of this type are often used in dusty areas. This dust easily clogs air actuated switches and prevents such switches from effectively limiting the twisting of the bucket. As a result of failure of such limit switches, buckets on these vehicles are frequently damaged because of stresses from excess tilting.
Therefore, a need exists for a load handling vehicle having a side tilt mechanism for a bucket which minimizes the stresses applied to the bucket during tilting.